The present invention relates to a semiconductor integrated circuit. In particular, it is suitable for use in a semiconductor integrated circuit with CMOS structure where a plurality of circuit blocks are integrated within a single chip and analog control lines are connected to each circuit block.
Technologies for manufacturing semiconductor devices include Si (silicon) bipolar technology, GaAs (gallium arsenide) technology for compound semiconductors, CMOS technology, and the like. Among such technologies, CMOS technology has the following characteristics: power consumption is small, it operates also low voltage, high-speed performance is possible by scale down, and the manufacturing costs are inexpensive, among other features. Thus, at present, this technology is the most commonly used among those for semiconductor devices.
Given such circumstances, bipolar technology or GaAs technology is used for a RF (Radio Frequency) circuit (analog circuit section) receiving and processing high frequency signals in many cases, and CMOS technology has hardly been used thus far. This is because CMOS technology is mainly suitable for digital circuits, and CMOS circuits could not acquire the sufficient high frequency characteristics where S/N is good.
However, in recent years, a semiconductor chip for Bluetooth for short-distance wireless data communication technology and wireless LAN using a 5 GHz band adopting CMOS technology have emerged. This is because for data communications are the main elements for Bluetooth and wireless LAN. This is different from cellular-phones and the like, voice calls are given the top priority. That is, regarding the Bluetooth and wireless LAN, the standard value of characteristics necessary for an RF circuit are less stringent than those for cellar-phones and the like. However, by advancing with the improvement of CMOS technology in the future, it is expected that CMOS technology will be also adopted to cellar-phones and the like.
Meanwhile, in recent years, high-integration and multi-functionalization have progressed regarding semiconductors, and many of ICs for which a plurality of circuit blocks are integrated within a single semiconductor chip have been provided. As such, when a plurality of circuit blocks are integrated into a single chip, it is desirable that the ON/OFF functions of the power source can be controlled independently for each individual circuit block for the purpose of reduction of electric power consumption and the like.
For example, as for a circuit where receiving functions of both AM radio broadcasting and FM radio broadcasting are integrated in a single chip, when receiving AM radio broadcasting, the circuit blocks for AM should be ON, and the circuit blocks for FM should be OFF. And when receiving FM radio broadcasting, the circuit blocks for AM should be OFF, and the circuit blocks for FM should be ON. In order to realize this, the power source should not be turned ON/OFF collectively outside the chip. On the contrary, a system where the ON/OFF functions of the power source can be controlled for each circuit block within the chip is required.
A conventional integrated circuit using bipolar transistors could realize enormous driving force, even for a small transistor. Thus, a transistor for switching was arranged at the root of each circuit block, and by controlling such transistor, ON/OFF functions of the power source could be switched.
However, as for the integrated circuit based on CMOS technology, the driving force of a MOSFET (metal-oxide semiconductor field-effect transistor) within such circuit is not as high. Therefore, a system where a transistor for switching is arranged only at the root of each circuit block cannot be adopted. Thus, as for CMOS technology, it is required that ON/OFF functions of the power source be individually controlled for individual transistors used within the circuit blocks. Inevitably, the number of transistors used for controlling the power source becomes increased.
Additionally, when the ON/OFF functions of the power source are controlled for individual transistors, a status of floating where no gate of transistors is connected to anywhere applies when OFF. Under such status, transistors become in a state of high impedance, which tends to receive noise. In some cases, an erroneous circuit might be operated as a result of noise. Therefore, a switching transistor that shuts down erroneous operations resulting from such noise is also required, and the number of transistors becomes further increased.
As such, regarding the IC chip based on CMOS that integrates a plurality of circuit blocks, many transistors are required so as to control the ON/OFF functions of the power source for every individual circuit block. Thus, the number of analog control lines used so as to supply control signals to such transistors becomes extremely increased. Naturally, when analog circuits are structured by CMOS technology, the number of analog control lines used so as to control circuit operation and as ON/OFF functions of the power source also becomes increased. As a result of this, the wiring area within the IC chip is increased.
In the previous CMOS process, in order to avoid maximization of chip size due to increasing the wiring area for control line, control lines were wired through use of multilayer wiring, in such a manner that the circuit blocks overlap in the upper layer or lower layer of the circuit blocks regarding the layout. FIG. 1 shows the example of a wiring layout in such a case.
The IC chip 100 shown in FIG. 1 is equipped with a circuit block 1 that performs processes unique to AM, a circuit block 2 that performs processes unique to FM, an AM/FM common circuit block 3 that performs common processes between AM and FM, and a control circuit 4. The analog control lines 105−1 to 105−3 are wired between all circuit blocks 1 to 3 and the control circuit 4.
As for an example of FIG. 1, the analog control line 105−1 that are wired from the control circuit 4 to the AM circuit block 1 and the analog control line 105−2 that are wired from the control circuit 4 to FM circuit block 2 are arranged over the top of the AM/FM common circuit block 3 (accurately, in a wiring layer different from the AM/FM common circuit block 3) in order to prevent the chip size from being larger in accordance with the wiring area.
However, when the analog control lines are wired over the top of the circuit block as such, the parasitic capacity is formed equally through an insulated layer by the signal lines within the circuit block and the analog control lines. As a result of this, the signal lines within the circuit block and analog control lines will become capacitively coupled.
Thus, signals are mutually transmitted and mutual interference occurs via the parasitic capacity between the signal lines and the analog control lines. This has resulted in a problem in that the quality of the analog signals flowing in the signal lines becomes deteriorated due to interference by the control signals superposed from the analog control lines. Additionally, this has caused another problem in that the control signals flowing in the analog control lines fluctuate due to the signals superposed from the signal lines, and erroneous operations have occurred.
In particular, in recent years, an analog/digital mixed LSI has been used in many cases, which is equipped with an analog circuit block and digital circuit block as a plurality of circuit blocks integrated on a single chip. In such analog/digital mixed LSI, when analog control lines are wired in the upper layer or lower layer of digital circuit block, digital signals with large voltage, such as clock signals, overlap minute analog control signals via parasitic capacity. This has tended to lead to a problem causing erroneous operation.
The purpose of the present invention is to resolve such problems. That is to say, when using CMOS technology and integrating a plurality of circuit blocks within a single chip, coupling noise arising through the analog control lines connected with each circuit block can be prevented, and deterioration of analog characteristics or erroneous operation of circuits can be suppressed.